Ubaidullah became a Muslim and married Umm Habiba, daughter of Abu
Sufyan. Both he and his wife joined the first band of persecuted
Muslims who sought refuge under the Christian King of Ethiopia
(Abyssinia) in 615AD.
Some time after coming to Ethiopia, he gave up Islam and
became a Christian, and testified his new faith to the other Muslim
refugees. Ubaidullah lived and died a Christian in Ethiopia. Muhammad
married his widow. Ibn Ishaq relates:

"`Ubaydullah went on searching until Islam came; then he migrated
with the Muslims to Abyssinia taking with him his wife who was a
Muslim, Umm Habiba, d. Abu Sufyan. When he arrived there he adopted
Christianity, parted from Islam, and died a Christian in Abyssinia.

Muhammad b. Ja`far b. al-Zubayr told me that when he had become a
Christian `Ubaydullah as he passed the prophet's companions who
were there used to say: We see clearly, but your eyes are only
half open, i.e. We see, but you are only trying to see and cannot
see yet. He used the word sa'sa' because when a puppy tries
to open its eyes to see, it only half sees. The other faqqaha
means to open the eyes. After his death the apostle married his
widow Umm Habiba."
(Ibn Ishaq, The Life of Muhammad, tr. Guillaume,
1967, p. 99)